Device and method for processing computer tomography imaging data

ABSTRACT

The invention relates to a device for processing CT imaging data, comprising a processing unit, which is configured to receive a plurality of sets of CT imaging data recorded at different imaging positions and at different points in time. Furthermore, the processing device is configured to provide a plurality of auxiliary sets of CT imaging data, each auxiliary set of CT imaging data comprising processed image data allocated to spatial positions inside a respective spatial section of the object space, wherein a given one of the spatial sections contains those spatial positions which are covered by those sets of CT imaging data acquired at a respective one of the imaging positions, and to generate the processed image data for a given spatial position using those of the sets of CT imaging data acquired at the respective one of the imaging positions.

FIELD OF THE INVENTION

The invention is related to a device for processing computer tomography(CT) imaging data, a CT imaging apparatus, a method for processing CTimaging data, a method for operating a CT imaging apparatus, a computerprogram for controlling a processing unit of a device for processingcomputer imaging data and to computer program for controlling operationof a CT imaging apparatus.

BACKGROUND OF THE INVENTION

Perfusion CT (PCT) is a technique for assessing information pertainingto the passage of fluid (e.g., blood, lymph, etc.) through anatomicaltissue to facilitate identifying a health state of the tissue or othertissue. It involves acquiring sequential images of an anatomicallocation after the injection of contrast material and allows obtainingvital functional physiology information. However, the anatomic coverageof this technique is per se relatively small. In order to increase theanatomical coverage and at the same time avoid requiring more scan timeand a larger amount of contrast material in multiple PCT scans, it isknown to operate a CT imaging apparatus in a jog mode. In the jog mode,a scanner table of the CT imaging apparatus is moved back and forthbetween different between neighboring but non-overlapping imagingpositions within a single study. Due to breathing motion or othermovement of a person or an object (organ, tissue, etc.) under study,gaps or overlaps between different sets of CT imaging data taken atdifferent imaging positions can occur. Thus, the CT imaging dataacquired at different times and different imaging positions may notrelate well since the size of a gap or overlap between the differentsets of CT imaging data acquired at different times and differentimaging positions is not known. The original advantage of the jog mode,i.e., a larger anatomic coverage may therefore not be fully achieved.

The publication N. K. G. Jensen et al., “Prediction and Reduction ofMotion Artifacts in Free-Breathing Dynamic Contrast Enhanced CTPerfusion Imaging of Primary and Metastatic Intrahepatic Tumors”,Academic Radiology, Vol. 20, No. 4, April 2013, pages 414 to 422,describes a method for predicting and reducing motion artifacts infree-breathing liver perfusion computed tomography (CT) scanning withcouch shuttling and to compare tumor and liver parenchyma perfusionvalues. A semiautomatic respiratory motion correction algorithm isapplied to align the acquired images along the z-axis. Perfusion mapsare generated using the dual-input Johnson-Wilson model. Root meansquared deviation (RMSD) maps of the model fit to the pixel time-densitycurves are calculated.

U.S. Pat. No. 9,002,089 B2 describes a method of registering a 4Dcontrast enhanced image data set. The four-dimensional (4D) contrastenhanced image data set covering three spatial dimensions and the timedimension includes image data of the same volume of interest acquired atdifferent time frames with changing contrast enhancement, the volume ofinterest includes moving structure, and the different time framescorrespond to a predetermined motion phase of interest in differentmotion cycles of the moving structure. The method comprises: registeringimage data corresponding to a plurality of different timeframes withreference image data from one of the timeframes. The image data and thereference image data correspond to a same volume of interest anddifferent time frames.

SUMMARY OF THE INVENTION

According to a first aspect of the invention, a device for processing CTimaging data is provided. The processing device comprises a processingunit, which is configured

to receive a plurality of sets of CT imaging data recorded at differentimaging positions and at different points in time, wherein each set ofCT imaging data comprises image data regarding a respective imagedfraction of an object space recorded from a respective imaging positionat a respective point in time, and coordinate data,

to provide a plurality of auxiliary sets of CT imaging data, eachauxiliary set of CT imaging data comprising processed image dataallocated to spatial positions inside a respective spatial section ofthe object space, wherein a given one of the spatial sections containsthose spatial positions which are covered by those sets of CT imagingdata acquired at a respective one of the imaging positions, and

to generate the processed image data for a given spatial position usingthose of the sets of CT imaging data acquired at the respective one ofthe imaging positions.

The device for processing CT imaging data of the first aspect of theinvention is herein also referred to as the processing device. Theprocessing device according to the first aspect of the invention usesthose sets of CT imaging data acquired at a given one of the imagingpositions to generate one of the auxiliary sets of CT imaging data. Thiscreates respective spatial section of the object space. The givenspatial section contains those spatial positions which are covered bythose sets of CT imaging data acquired at the given one of the imagingpositions. The processing device generates processed image data for thespatial positions inside this spatial section covered by these sets ofCT imaging data. Since the sets of CT imaging data acquired at therespective one of the imaging positions are recorded at different pointsin time, they typically comprise image data acquired at different phasesof a periodic motion of the imaged fraction of the object space. Anexample for such a periodic motion in the field of CT perfusion imagingis the respiration motion of the person or object. This is used toadvantage by the processing device of the present invention by providingthe processed image data over larger volume of the spatial positions,namely, a volume spanned by the total set of images (sets of CT imagingdata) taken at this imaging position. For each spatial section of theobject space can be described as defined by an outer envelope of allspatial positions covered by any of the sets of registered CT imagingdata recorded at a given imaging position. In other words, a givenauxiliary set of CT imaging data covers any spatial position covered byany of the sets of CT imaging data recorded at the given imagingposition. As a result, a larger imaged volume can be visualized for agiven one of the imaging positions.

Furthermore, image artifacts that in prior-art solutions may occur dueto motion of the imaged fraction of the object space can be reduced oreliminated in the processed image data. Generating the processed imagedata for a given spatial position using those of the sets of CT imagingdata acquired at the respective one of the imaging positions allowscompensating the mentioned detrimental motion effects.

Thus, the processing device allows achieving an improved visualizationof CT imaging data acquired from a given object at different points intime, such as in a jog mode of operation. This improves the performanceof application scenarios such as a 4D CT perfusion analysis.

In the following, embodiments of the device for processing CT imagingdata according to the first aspect of the invention will be described.

An imaged fraction of the object that corresponds to a given set of CTimaging data can be either a two-dimensional plane or, as it is mostlythe case in CT imaging, a three-dimensional volume.

Coordinate data can take different forms. In one example, they allow anallocation of the respective image data to respective spatial positionswithin the imaged fraction of the object space. In some suchembodiments, the coordinate data provides a reference toreal-world-coordinates and therefore allow an allocation to absolutepositions of the imaged object space. In other embodiments, however, thecoordinate data provides a relative reference, thus only allowing anallocation to relative positions, in particular having a relativereference within the given plurality of auxiliary sets of CT imagingdata. This is sufficient for instance where a user is able to identifythe imaged region by the features visible in the auxiliary sets of CTimage data.

To provide such absolute or relative coordinate data, one embodiment ofthe processing unit is configured to perform, before assembling theauxiliary sets of CT imaging data, a registration of the respective setsof CT imaging data so as to provide registered auxiliary sets of CTimaging data. The processing device of this variant allows an assemblingof these registered auxiliary sets of CT imaging data to form a singleset of auxiliary CT imaging data. This single set typically is two- orthree-dimensional representation of the imaged object and does not allowvisualizing the imaged as a function of time. Registration can beperformed by using methods which per se are known in the art, such asregistration to a certain reference frame or simultaneous registration.

In one example of such embodiments, the processing unit is configured

to receive the sets of CT imaging data recorded at different imagingpositions and at different points in time as unregistered CT imagingdata, and

to assign to the image data respective coordinates which provide anallocation to spatial positions of the respective imaged fractions ofthe object space, so as to form and provide for each set of unregisteredCT imaging data a corresponding set of registered CT imaging data.

In this embodiment, thus, the processing unit is configured to registerunregistered sets of CT imaging data on its own, and does not rely onprevious registration of the CT imaging data by an external device.

The respective coordinates of the image data of a respective set ofregistered CT imaging data comprise in one variant of this embodiment asone component of the coordinates an allocation of the image data to itsrespective imaging position. Furthermore, in a variant of thisembodiment the respective further coordinate components assigned to theimage data of a respective set of registered CT imaging data areindicative of relative positions within the given set of CT imagingdata.

A given auxiliary set of CT imaging data in a state after registration,but before generating the processed image data, may be visualized as anoverlay of a plurality of individual sets (frames) of CT imaging datataken at the same imaging position, wherein the different frames may beshifted, deformed and/or rotated with respect to each other, dependingon the effects of patient motion during the image acquisition. Inregions of large overlay, i.e., where a large number of individualframes cover the same fraction of the object space, a correspondingnumber of different frames can be used to generate the processed imagedata. In other regions with less overlap, the data basis for generatingthe processed image data is smaller.

In an embodiment of the processing device the processing unit is furtherconfigured to assemble the respective auxiliary sets of CT imaging dataso as to form a single set of auxiliary CT imaging data combining thespatial sections of the object space. This form of assembling imagingdata is also referred to as stitching.

The single set of auxiliary CT imaging data comprises imaging dataregarding all imaged fractions of the object space and thus provides alarge volume of object coverage. Since each one of the combinedauxiliary sets of CT imaging data is formed by processing a plurality ofsets of CT imaging data, image artifacts of respective sets of CTimaging data have a reduced impact on the resulting single set ofauxiliary CT imaging data.

Due to object motion during the acquisition of a time series as in 4D CTperfusion studies, auxiliary sets of CT imaging data taken atneighboring imaging positions may cover overlapping spatial sections ofthe object space. This is used to advantage in one embodiment, in whichthe processing unit is configured, in assembling the respectiveauxiliary sets of CT imaging data,

to determine whether at least two of the spatial sections comprise anidentical overlapping section of the object space, and

to generate the processed image data for a given spatial positionadditionally using those sets of CT imaging data acquired at other thanthe respective one of the imaging positions and comprising at least someimaging data allocated to spatial positions inside the given spatialsection of the object space.

For instance, in a situation where the processed image data for spatialpositions covered by sets of CT imaging data acquired at neighboringimaging positions, the processed image data for such spatial positionsfalling into the overlap is generated from both sets. Thus, an improvedquality of processed image data and an improved assembling or stitchingof the respective auxiliary sets of CT imaging data is achieved.

In a further embodiment, the processing device further comprises aregistration unit, which is configured

to receive the sets of CT imaging data recorded at different imagingpositions and at different points in time as unregistered CT imagingdata, and

to assign to the image data respective coordinates which provide theallocation to spatial positions of the respective imaged fractions ofthe object space, so as to form and provide for each set of unregisteredCT imaging data the corresponding set of registered CT imaging data, and

to provide the sets of registered CT imaging data to the processing unitfor use as the sets of CT imaging data, from the auxiliary sets arederived.

In this embodiment, the processing device has a registration unitseparate from the processing unit and also does not rely on previousexternal registration of the CT imaging data.

In a variant of this embodiment, the coordinates are spatialcoordinates. In a further variant, the coordinates indicate a phase of aperiodic respiration motion of the object, which enables in combinationwith information concerning the respective imaging position anallocation to spatial positions. In another variant, the coordinates arederived by a comparison between the imaged fraction of the object spaceand a predetermined reference fraction of the object space, wherein eachpredetermined reference fraction corresponds to exactly one imagingposition. This variant additionally requires a receiving of thepredetermined reference fractions that correspond to the object, by theregistration unit. In an example of this variant, each predeterminedreference fraction is a single set of CT imaging data recorded at acorresponding imaging position. For instance, registration of the setsof CT imaging data acquired at a given one of the imaging positions isperformed with respect to a reference set of CT imaging data, which isformed by either the first set acquired at this imaging position (i.e.,at the earliest point in time). Another example is the use ofsimultaneous registration.

In another embodiment of the processing device, the processing unit isconfigured to generate the auxiliary CT imaging data for a given spatialposition by performing an averaging using image data from thoseregistered sets of CT imaging data covering the given spatial position.In a variant of this embodiment, the averaging comprises an averaging ofa grayscale tone value of the image data. Such an averaging is in afirst example an arithmetical averaging of the grayscale tone values. Ina further example, just grayscale tone values below a certainpredetermined tone threshold distance from a mean grayscale tone valueare used for the averaging. By averaging, an impact of image artifacts,e.g., due to motion, can be reduced.

In another embodiment the processing unit is configured to generate theauxiliary CT imaging data for a given spatial position by determiningand selecting from that image data allocated to the given spatialposition and comprised in different sets of CT imaging data either amaximum tone value or a minimum tone value. The determining of a minimumor maximum tone value in this embodiment allows the auxiliary sets of CTimaging data to provide image data with a higher contrast.

In a further embodiment, the processing device is further configured toprovide sets of registered CT imaging data, each set comprising imagingtime information, which is indicative of a temporal order of the sets ofregistered CT imaging data with respect to the points in time at whichthe corresponding sets of CT imaging data have been recorded. Thus, inthis embodiment, the processing device provides sets of registered CTimaging data that can be used to generate time resolved sequences of animaged fraction of the object space.

In a further embodiment, the processing device is further configured toreceive a user input information indicative of a chosen processingscheme for generating the auxiliary CT imaging data for a given spatialposition, wherein the chosen processing scheme is one of the group of anaveraging using corresponding image data, a selecting of maximum tonevalues, or a selecting of minimum tone values. In this embodiment, auser can determine or switch the processing scheme for generating theauxiliary CT imaging data and thus adapt the processing scheme to theimaged object space. Furthermore, the user can select and use alldifferent processing schemes to compare the image information accordingto the differently generated sets of auxiliary CT imaging data forobtaining more information for image analysis.

The processing device can be provided in the form of a hardware modulewith dedicated circuitry or as a programmable processor with suitableexecutable software code. This allows updating or upgrading a prior-artCT imaging apparatus so as to additionally provide the functionalitydisclosed herein.

According to a second aspect of the invention, the invention relates toa CT imaging apparatus, comprising a CT image acquisition unit, which isconfigured to generate and provide a plurality of sets of CT imagingdata recorded at different imaging positions and at different points intime, wherein each set of CT imaging data comprises image data regardinga respective imaged fraction of an object space recorded from arespective imaging position at a respective point in time, andcoordinate data, and a device for processing CT imaging data accordingto the first aspect of the invention or one of its embodiments.

The CT imaging apparatus according to the second aspect of the inventionshares the advantages of the processing device according to the firstaspect of the invention.

The CT imaging apparatus according to the second aspect of the inventioncomprises a data connection for providing the sets of CT imaging data,which are later on processed by the device for processing CT imagingdata. In an embodiment, the data connection is provided via a cable. Inanother embodiment, the data connection is provided wireless or by meansof a manually exchangeable memory.

In a further embodiment the CT imaging apparatus comprises a controlprocessor, which is configured to control an acquisition of the sets ofCT imaging data by the CT image acquisition unit in a jog mode ofoperation by periodically moving the CT image acquisition unit toimaging positions of a predetermined set of imaging positions andtriggering acquisition of a respective set of CT imaging data from agiven imaging position before moving to the next imaging position. TheCT imaging apparatus of this embodiment thus allows a controlledrecording of sets of CT imaging data at different imaging positions andat different points in time, as required by the device for processing CTimaging data for generating the processed image data as described above.In a variant of this embodiment, the CT image acquisition unit can becontrolled to trigger the acquisition of respective sets of CT imagingdata more often at imaging positions that are of higher importance for auser of the CT imaging apparatus. In a further variant of thisembodiment, the CT image acquisition unit is mounted below a moveabletable, which is moved back and forth for periodically changing theimaging positions. In this variant, the corresponding imaging positionscan be reproduced precisely by moving the table with the CT imageacquisition unit to respective predetermined positions.

In another embodiment of the CT imaging apparatus, the CT imageacquisition unit is further configured to determine for each set of CTimaging data respective imaging time information, which is indicative ofa point in time when the respective set of CT imaging data has beenrecorded. In a variant of this embodiment, the determining and aproviding of the imaging time information is advantageous for theassigning of respective coordinates which provide an allocation tospatial positions to the image data. In this variant, the phase of aperiodic motion of the object is determined as respective coordinate, byconsidering the periodic motion according to the imaging timeinformation.

In a further embodiment of the CT imaging apparatus, a user inputinterface is provided, which is arranged and configured to receive userinput information indicative of a user-selected processing scheme forgenerating the auxiliary CT imaging data. As described before, theprocessing scheme is for instance one of the group of an averagingprocess, a selection of maximum tone values, or a selection of minimumtone values.

In an embodiment of the CT imaging apparatus, the CT imaging devicefurther comprises an output unit, arranged to receive the single set ofauxiliary CT imaging data and to output the single set of auxiliary CTimaging data as a graphical output for visualization. Preferably, theoutput unit has a display configured to output the single set ofauxiliary CT imaging data. In a further variant, the output unit isconfigured to provide a the graphical output in the form of a print-out.

According to a third aspect of the invention, the invention relates to amethod for processing CT imaging data. The method comprises

receiving a plurality of sets of CT imaging data recorded at differentimaging positions and at different points in time, wherein each set ofCT imaging data comprises image data regarding a respective imagedfraction of an object space recorded from a respective imaging positionat a respective point in time, and coordinate data,

providing a plurality of auxiliary sets of CT imaging data, eachauxiliary set of CT imaging data comprising processed image dataallocated to spatial positions inside a respective spatial section ofthe object space, wherein a given one of the spatial sections containsthose spatial positions which are covered by those sets of CT imagingdata acquired at a respective one of the imaging positions, and

generating the processed image data for a given spatial position usingthose of the sets of CT imaging data acquired at the respective one ofthe imaging positions.

The method according to the third aspect of the invention shares theadvantages of the processing device according to the first aspect of theinvention.

In an embodiment of the method, the method further comprises the step ofassembling the respective auxiliary sets of CT imaging data so as toform a single set of auxiliary CT imaging data combining the spatialsections of the object space.

In a further embodiment of the method according to the fourth aspect ofthe invention, the assembling of the respective auxiliary sets of CTimaging data comprises

determining whether at least two of the spatial sections comprise anidentical overlapping section of the object space, and

generating the processed image data for a given spatial positionadditionally using those sets of CT imaging data acquired at other thanthe respective one of the imaging positions and comprising at least someimaging data allocated to spatial positions inside the given spatialsection of the object space.

According to a fourth aspect of the invention, a method for operating aCT imaging apparatus is provided, comprising

controlling a CT image acquisition unit of the CT imaging apparatus ingenerating and providing a plurality of sets of CT imaging data atdifferent imaging positions and at different points in time, whereineach set of CT imaging data comprises image data regarding a respectiveimaged fraction of an object space recorded from a respective imagingposition at a respective point in time, and coordinate data, and

processing the CT imaging data according the method of the third aspectof the invention.

The method according to the fourth aspect of the invention shares theadvantages of the processing device according to the first aspect of theinvention.

According to a fifth aspect of the invention, the invention relates to acomputer program for controlling a processing unit of a device forprocessing computer tomography imaging data, comprising program codemeans for causing the processing unit to carry out a method according tothe third aspect of the invention or one of its embodiments.

According to a sixth aspect of the invention, the invention relates to acomputer program for controlling operation of a CT imaging apparatus,comprising program code means for causing a control processor of the CTimaging apparatus to control operation of the CT imaging apparatus inaccordance with a method according to the fourth aspect of theinvention.

The processing unit or control processor for instance forms anintegrated part of a CT imaging apparatus and can be implemented as amicrocontroller or as a microprocessor. In another embodiment, theprocessing unit or control processor forms is not part of CT imagingapparatus, but for instance an integrated part of a hospital computersystem for analyzing previously acquired CT imaging data.

It shall be understood that the device for processing CT imaging data ofthe first aspect of the invention, also defined in claim 1, the CTimaging device of the second aspect, also defined in claim 7, the methodfor processing CT imaging data of the third aspect, also defined inclaim 9, the method for operating a CT imaging apparatus of the fourthaspect of the invention, also defined in claim 12, the computer programfor controlling a processing unit of a device for processing computertomography imaging data of the fifth aspect, also defined in claim 13,and the computer program for controlling operation of a CT imagingapparatus of the sixth aspect of the invention, also defined in claim14, have similar or identical embodiments.

Further embodiments will be described below with reference to theenclosed drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

In the following drawings:

FIG. 1 shows a first embodiment of a device for processing CT imagingdata according to a first aspect of the invention;

FIG. 2 shows a second embodiment of the device for processing CT imagingdata according to the first aspect of the invention;

FIG. 3a shows a scheme for generating auxiliary CT imaging data byaveraging tone information according to the first aspect of theinvention;

FIG. 3b shows a scheme for generating auxiliary CT imaging data bystoring maximal values of the tone according to the first aspect of theinvention;

FIG. 3c shows a scheme for generating auxiliary CT imaging data bystoring minimal values of the tone according to the first aspect of theinvention;

FIG. 4 shows an embodiment of a CT imaging apparatus according to asecond aspect of the invention;

FIG. 5 shows a block diagram of a first embodiment of a method forprocessing CT imaging data according to a third aspect of the invention;

FIG. 6 shows a block diagram of a second embodiment of the method forprocessing CT imaging data according to the third aspect of theinvention;

FIG. 7 shows a block diagram of a third embodiment of the method forprocessing CT imaging data according to the third aspect of theinvention;

FIG. 8 shows a block diagram of an embodiment of a method for operatinga CT imaging apparatus according to a fourth aspect of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

FIG. 1 shows a first embodiment of a device for processing CT imagingdata 100. The device for processing CT imaging data, hereinafterprocessing device 100 comprises a registration unit 110 which isconfigured to receive sets of CT imaging data recorded at differentimaging positions and at different points in time as unregistered CTimaging data 120. The registration unit 110 is further configured toassign to the image data respective coordinates which provide anallocation to spatial positions of the respective imaged fractions 125of the object space, so as to form and provide for each set ofunregistered CT imaging data 120 a corresponding set of registered CTimaging data 135, and to provide the sets of registered CT imaging datato a processing unit 140, as indicated by an arrow 130.

The processing unit 140 is configured to receive a plurality of the setsof registered CT imaging data 135 and to generate and provide aplurality of auxiliary sets of CT imaging data 160, each auxiliary setof CT imaging data 160 being allocated to a spatial position inside arespective spatial section of the object space, wherein a given one ofthe spatial sections contains those spatial positions which are coveredby those sets of registered CT imaging data 135 acquired at a respectiveone of the imaging positions.

Furthermore, the processing unit 140 is configured to generate theprocessed image data for a given spatial position using those of thesets of registered CT imaging 135 data acquired at the respective one ofthe imaging positions. The total number of auxiliary sets of CT imagingdata is thus equal to the number of imaging positions used during theoriginal acquisition of the sets of CT imaging data. For sets acquiredin a jog mode of operation, such overlaying of sets of CT imaging dataaccording to their respective imaging position will typically find astrong overlap of the acquired sets in a center fraction of the overallvolume covered by the sets acquired at a given imaging position, whilein boundary regions of that overall volume image data from less setswill be available. This is due to the issue of object motion describedearlier. Thus, a given set of auxiliary CT imaging data covers anenvelope volume containing all volumes covered by the original setsacquired at the given imaging position.

The auxiliary sets of CT imaging data 160 are provided forvisualization, for instance on a display, as indicated by an arrow 150.

FIG. 2 shows a second embodiment of a device for processing CT imagingdata 200 according to the first aspect of the invention.

The processing device 200 is similar to the device for processing CTimaging data 100 shown in FIG. 1, but in addition, the depicted secondembodiment comprises a stitching unit 250 and a user interface 270.

The stitching unit 250 forms a part of the processing unit 240 and isconfigured to receive the auxiliary sets of CT imaging data 150, whichwere generated as described in the context of FIG. 1. After receivingthe auxiliary sets of registered CT imaging data 150, the stitching unit250 assembles the respective auxiliary sets of CT imaging data 150 so asto form a single set of auxiliary CT imaging data 260, combining thespatial sections of the object space. For this step the informationderivable from the auxiliary sets with respect to their positionrelative to each other is used. From this and the prior registration theposition of each auxiliary set relative to the object, e.g., the patientcan be determined. Finally, the correctly assembled auxiliary set of CTimaging data 260 is provided by the stitching unit 250.

Depending on the exact volume coverage of the auxiliary sets, theassembled auxiliary set may contain one or more gaps, for which no imagedata is available. To avoid gaps, one variant uses predetermined imagingpositions selected to guarantee a minimum overlap of spatial positionsof the object space covered.

However, overlaps between the auxiliary sets are not desired in theassemble set of processed image data after stitching. They can beremoved by the stitching unit. This is in one variant achieved bygenerating the processed image data for a given spatial positionadditionally using additionally those sets of CT imaging data acquiredat other than the respective one of the imaging positions and comprisingat least some imaging data allocated to spatial positions inside thegiven spatial section of the object space. To avoid unnecessary doublecomputation based on such overlapping image information for differentauxiliary sets covering the overlap, the respective spatial positionsare excluded from one of the concerned auxiliary sets of CT imaging dataso as to provide a seamless assembled set.

As a further difference in comparison to the device for processing CTimaging data 100 that is shown in FIG. 1, the embodiment depicted inFIG. 2 comprises the user input interface 270, which is arranged andconfigured to receive a user input 280 and to internally provide userinput information 290. The user input 280 is indicative of a selectedprocessing scheme for generating the auxiliary sets of CT imaging datafor a given spatial position. The user input 280 in the embodiment ofFIG. 2 is possible by means of a touch screen 295. In other embodimentsnot shown, the user input is provided by operation of a switch orbuttons. The chosen processing scheme is for instance one of the groupcomprising an averaging using corresponding image data 282, a selectingof maximum tone values 284, or a selecting of minimum tone values 286.Other known processing schemes that combine the image data gathered atdifferent times at the respective imaging position may of course beused.

FIG. 3a, 3b, 3c illustrate different alternative schemes for generatingthe processed image data, each scheme using, by way of example, astrongly simplified grey tone scale.

FIG. 3a shows a scheme for generating processed image data by averagingtone information. The averaging process is shown for four spatialpositions 312, 314, 316, 318 with a first set of CT imaging dataindicative of a tone of the spatial positions 312′, 314′, 316′, 318′ anda second set of CT imaging data indicative of the tone of the spatialpositions 312″, 314″, 316″, 318″. A black tone provided with the firstset of CT imaging data for the spatial position 312′ is averaged with awhite tone of the corresponding spatial position 312″ to a resultinggrey tone of the spatial position 312 provided by the auxiliary set ofregistered CT imaging data. The further spatial positions 314, 316, 318are averaged analogously.

FIG. 3b shows a further scheme for generating auxiliary registered CTimaging data, involving determining and selecting maximal tone values.In contrast to the averaging process described in FIG. 3a , generating atone for the spatial position 322 by determining and selecting maximumtone values comprises comparing a black tone and a white tone of thecorresponding spatial positions 312′ and 312″ indicated by the first andsecond set of CT imaging data. As a result, the present scheme leads toselection of the black tone of the spatial position 322 in the auxiliaryset of registered CT imaging data, since black forms a maximum tonevalue on the grey tone scale.

FIG. 3c shows a further scheme for generating auxiliary registered CTimaging data, involving determining and selecting minimal tone values.In contrast to the averaging process described in FIG. 3a , generating atone of the spatial position 332 by determining and selecting minimaltone value leads to a white tone of the spatial position 332 provided bythe auxiliary set of registered CT imaging data, since white is theminimal tone value.

FIG. 4 shows an embodiment of a CT imaging apparatus 400. The CT imagingapparatus 400 comprises a CT image acquisition unit 410, which isconfigured to generate and provide a plurality of sets of CT imagingdata recorded at different imaging positions 412, 414, 416, 418 and atdifferent points in time by moving from imaging position to imagingposition. The CT image acquisition unit 410 is mounted below a moveabletable 430 so as to image a patient or object 440 positioned on thetable. The different imaging positions thus correspond to differentpositions of the table 430 with respect to the CT image acquisition unit410. The overall number and exact positions of the imaging positions canbe determined by a user prior to operation of the CT imaging apparatusaccording to the given imaging task. A relative position of the CT imageacquisition unit 410 with respect to the table 430 is controlled by acontrol processer 435. The control processor 435 is configured tocontrol an acquisition of the sets of CT imaging data by the CT imageacquisition unit 410. In particular, one provided option for operationis a jog mode of operation for performing CT perfusion studies. The jogmode involves periodically toggling the relative position of the CTimage acquisition unit 410 with respect to the moveable table 430,stopping at the imaging positions 412, 414, 416, 418 for a predeterminedtime span (for example 4 seconds) and acquiring a respective set of CTimaging data at each stop during this time span.

The CT imaging apparatus comprises a device for processing CT imagingdata, which in this non-limiting example is the processing device 200described above in the context of FIG. 2. The sets of CT imaging dataare provided to the processing device 450 via a suitable data connection450.

For visualization in one of a plurality of modes of operation providedby the CT imaging apparatus 400, the processing device 200 delivers theassembled set of auxiliary CT imaging data via a suitable dataconnection 260 to an output unit in the form of a display device 460.The display device 460 is configured to provide a graphical output 470of the assembled single set of auxiliary CT imaging data 260 on a screen465.

FIG. 5 shows a flow diagram of a first embodiment of a method forprocessing CT imaging data according to a third aspect of the invention.

The method comprises a step 510 of receiving sets of CT imaging datarecorded at different imaging positions and at different points in time,wherein each set of CT imaging data comprises image data regarding arespective imaged fraction of an object space recorded from a respectiveimaging position at a respective point in time, and coordinate data.

A subsequent step 520 comprises a grouping of those respective sets ofCT imaging data which are acquired at a given one of the imagingpositions. A given group thus contains those sets of CT imaging datawhich were acquired at one imaging position.

In a subsequent step 530, the method proceeds with generating theprocessed image data for a given spatial position based on thepreviously performed grouping. In particular, a given group of those ofthe sets of CT imaging data acquired at the respective one of theimaging positions is used to determine the processed image data for agiven spatial position covered by the given group. As described above,generating of the processed image data for a given spatial position forinstance comprises an averaging of tone information or a selecting ofmaximal tone values or a selecting of minimal tone values according tothe corresponding CT imaging data of the sets of registered CT imagingdata.

FIG. 6 shows a flow diagram of a second embodiment of the method forprocessing CT imaging data. In addition to the steps 510 to 530 of themethod shown in FIG. 5, the method of FIG. 6 comprises a stitching step610, comprising assembling the auxiliary sets of CT imaging data so asto form a single set of auxiliary CT imaging data combining theircovered spatial sections of the object space. Through the achievedknowledge of the relative position of the volumes covered by theauxiliary sets relative to each other and the knowledge of the positionof each original set of CT imaging data within the given volume, therelative position of all volumes to each other is known and they can beassembled correctly. In particular, temporally averaged or interpolatedauxiliary sets of CT imaging data can thus be combined to form a volumeshowing the entire field of view. In the case of no overlap between theauxiliary sets of CT imaging data, necessary gaps between the imagescorresponding to the auxiliary sets are introduced by the presentmethod. It is an advantage of this method that the finally displayedvolumes of image data in the form of voxels at each spatial positioncorrespond and can be used directly to estimate the perfusionvoxel-wise.

FIG. 7 shows a flow diagram of a third embodiment of the method forprocessing CT imaging data. The method includes a particular stitchingapproach. In addition to the steps 510 to 530 of the method of FIGS. 5,two additional steps are performed in the context of stitching. A step710 comprises determining whether at least two of the spatial sectionscovered by a given pair of auxiliary sets of CT imaging data comprise anidentical overlapping section of the object space. A step 720 comprisesgenerating the processed image data for a given spatial position byadditionally using those sets of CT imaging data acquired at other thanthe respective one of the imaging positions. Such sets of CT imagingdata thus comprise at least some imaging data allocated to spatialpositions inside the given spatial section of the object space, which isalso covered from another imaging position, typically a neighboringimaging position. For the example of averaging, this embodiment uses thedetermined overlap to include all image data available for a givenspatial position in the determination of the averaged processed imagedata for this spatial position meant for display.

It is noted that for the purpose of viewing on a display or printout,the auxiliary sets are preferably deformed by rigid transformationsonly, i.e., translation or rotation, since in general doctors preferseeing the original over non-rigidly deformed images. In a furtherembodiment, however, deformed images obtained by the registration arefused if suitable for the given viewing application.

FIG. 8 shows a block diagram of an embodiment of a method for operatinga CT imaging apparatus according to a fourth aspect of the invention.The method a step 810 of controlling a CT image acquisition unit of theCT imaging apparatus in generating and providing a plurality of sets ofCT imaging data at different imaging positions and at different pointsin time. As described before, each set of CT imaging data comprisesimage data regarding a respective imaged fraction of an object spacerecorded from a respective imaging position at a respective point intime, and coordinate data. A step 820 comprises processing the CTimaging data according to the method shown in one of the FIGS. 5 to 7.

In summary, the invention relates to a device for processing CT imagingdata, comprising a processing unit, which is configured to receive aplurality of sets of CT imaging data recorded at different imagingpositions and at different points in time, wherein each set of CTimaging data comprises image data regarding a respective imaged fractionof an object space. Furthermore, the processing device is configured toprovide a plurality of auxiliary sets of CT imaging data, each auxiliaryset of CT imaging data comprising processed image data allocated tospatial positions inside a respective spatial section of the objectspace, wherein a given one of the spatial sections contains thosespatial positions which are covered by those sets of CT imaging dataacquired at a respective one of the imaging positions, and to generatethe processed image data for a given spatial position using those of thesets of CT imaging data acquired at the respective one of the imagingpositions.

The invention is not limited to the disclosed embodiments. In particularthe invention is not restricted to a use within a CT imaging device. Anyreference signs in the claims should not be construed as limiting thescope.

1. A device for processing computer tomography imaging data, hereinafterCT imaging data, the processing device comprising a processing unitwhich is configured to receive a plurality of sets of CT imaging datarecorded at different imaging positions and at different points in time,wherein each set of CT imaging data comprises image data regarding arespective imaged fraction of an object space recorded from a respectiveimaging position at a respective point in time, and coordinate data, toprovide a plurality of auxiliary sets of CT imaging data, each auxiliaryset of CT imaging data comprising processed image data allocated tospatial positions inside a respective spatial section of the objectspace, wherein a given one of the spatial sections contains thosespatial positions which are covered by those sets of CT imaging dataacquired at a respective one of the imaging positions, and to generatethe processed image data for a given spatial position using those of thesets of CT imaging data acquired at the respective one of the imagingpositions.
 2. The device of claim 1, wherein the processing unit isfurther configured to assemble the respective auxiliary sets of CTimaging data so as to form a single set of auxiliary CT imaging datacombining the spatial sections of the object space.
 3. The device ofclaim 2, wherein the processing unit is configured, in assembling therespective auxiliary sets of CT imaging data, to determine whether atleast two of the spatial sections comprise an identical overlappingsection of the object space, to generate the processed image data for agiven spatial position additionally using those sets of CT imaging dataacquired at other than the respective one of the imaging positions andcomprising at least some imaging data allocated to spatial positionsinside the given spatial section of the object space.
 4. The device ofclaim 1, further comprising a registration unit, which is configured toreceive the sets of CT imaging data recorded at different imagingpositions and at different points in time as unregistered CT imagingdata, to assign to the image data respective coordinates which providean allocation to spatial positions of the respective imaged fractions ofthe object space, so as to form and provide for each set of unregisteredCT imaging data a corresponding set of registered CT imaging data, andto provide the sets of registered CT imaging data to the processingunit.
 5. The device of claim 1, wherein the processing unit isconfigured to generate the auxiliary CT imaging data for a given spatialposition by performing an averaging using image data from thoseregistered sets of CT imaging data covering the given spatial position.6. The device of claim 1, wherein the image data comprises a tone value,and wherein the processing unit is configured to generate the auxiliaryCT imaging data for a given spatial position by determining andselecting from that image data allocated to the given spatial positionand comprised in different sets of CT imaging data either a maximum tonevalue or a minimum tone value.
 7. The device of claim 1, which isfurther configured to provide sets of registered CT imaging data, eachset additionally comprising imaging time information, which isindicative of a temporal order of the sets of registered CT imaging datawith respect to the point in time at which the corresponding sets of CTimaging data have been recorded.
 8. A CT imaging apparatus, comprising aCT image acquisition unit which is configured to generate and provide aplurality of sets of CT imaging data recorded at different imagingpositions and at different points in time, wherein each set of CTimaging data comprises image data regarding a respective imaged fractionof an object space recorded from a respective imaging position at arespective point in time, and coordinate data, and a device forprocessing CT imaging data according to claim
 1. 9. The CT imagingapparatus of claim 8, comprising a control processor, which isconfigured to control an acquisition of the sets of CT imaging data bythe CT image acquisition unit in a jog mode of operation by periodicallymoving the CT image acquisition unit to imaging positions of apredetermined set of imaging positions and triggering acquisition of arespective set of CT imaging data from a given imaging position beforemoving to the next imaging position.
 10. A method for processingcomputer tomography imaging data, hereinafter CT imaging data,comprising receiving a plurality of sets of CT imaging data recorded atdifferent imaging positions and at different points in time, whereineach set of CT imaging data comprises image data regarding a respectiveimaged fraction of an object space recorded from a respective imagingposition at a respective point in time, and coordinate data, providing aplurality of auxiliary sets of CT imaging data, each auxiliary set of CTimaging data comprising processed image data allocated to spatialpositions inside a respective spatial section of the object space,wherein a given one of the spatial sections contains those spatialpositions which are covered by those sets of CT imaging data acquired ata respective one of the imaging positions, and generating the processedimage data for a given spatial position using those of the sets of CTimaging data acquired at the respective one of the imaging positions.11. The method of claim 10, further comprising assembling the respectiveauxiliary sets of CT imaging data so as to form a single set ofauxiliary CT imaging data combining the spatial sections of the objectspace.
 12. The method of claim 11, wherein assembling the respectiveauxiliary sets of CT imaging data comprises determining whether at leasttwo of the spatial sections comprise an identical overlapping section ofthe object space, generating the processed image data for a givenspatial position additionally using those sets of CT imaging dataacquired at other than the respective one of the imaging positions andcomprising at least some imaging data allocated to spatial positionsinside the given spatial section of the object space.
 13. A method foroperating a CT imaging apparatus, comprising controlling a CT imageacquisition unit of the CT imaging apparatus in generating and providinga plurality of sets of CT imaging data at different imaging positionsand at different points in time, wherein each set of CT imaging datacomprises image data regarding a respective imaged fraction of an objectspace recorded from a respective imaging position at a respective pointin time, and coordinate data, and processing the CT imaging dataaccording to the method of claim
 10. 14. A computer program forcontrolling a processing unit of a device for processing computertomography imaging data, comprising program code means for causing theprocessing unit to carry out a method according to claim
 10. 15. Acomputer program for controlling operation of a CT imaging apparatus,comprising program code means for causing a control processor of the CTimaging apparatus to control operation of the CT imaging apparatus inaccordance with a method according to claim 13.